House-broken animals, such as cats, are trained into the habit of urinating and defecating in a specially provided litter box. Similarly, untrained and caged animals, such as guinea pigs, urinate and defecate on the floor of their cage, often in approximately the same floor area of the cage. Consequently, pet owners, homeowners, veterinarians and laboratory personnel have added absorbent materials to the litter box or cage to collect the urine and feces.
The dross-soiled absorbent must be regularly cleaned to maintain a hygienic environment and to thwart the emission of objectionable odors from the presence of the urine and fecal matter in the litter. Removal of fecal matter from any litter is somewhat easy as they are generally solid objects that can be physically removed from the litter. However, physical removal of the feces does not address the issues of removing liquid dross from the litter nor does it help reduce or eliminate odors caused by the urine absorbed into the absorbent. Thus it can be said that the removal of the liquid dross from the litter is harder to execute.
Though the absorbent material aids in absorbing liquid dross, it does nothing to aid in the removal of the liquid dross and to identify the liquid dross in the litter. Therefore, when the odors caused by the absorbed urine become intolerable, the homeowner discards the litter box absorbent material entirely. The homeowner then washes the litter box and refills the litter box with fresh litter box absorbent material. These activities are unpleasant, time-consuming and expensive. Consequently, the litter box absorbent material usually is a relatively inexpensive solid absorbent material, such that an individual cleaning of the litter box is not particularly economically burdensome. However, repeated litter box cleanings over a period of time accounts for relatively large expenditures.
The most commonly used litter box absorbent materials are inexpensive clays, such as calcined clays, that are safe and non-irritating to the animals, and that absorb relatively substantial amounts of liquids. Other porous, solid litter box absorbent materials, that are used alone or in combination, include straw, sawdust, wood chips, wood shavings, porous polymeric beads, shredded paper, sand, bark, cloth, ground corn husks, cellulose, and water-insoluble inorganic salts, such as calcium sulfate. Each of these absorbent materials has the advantage of low cost, but each suffers from the disadvantage of merely absorbing a liquid waste product and holding the product within its porous matrices, or, in the case of sand, adsorbing the liquid dross on its surface. For each absorbent material, offensive odors are eventually caused by the absorbed urine, and the entire contents of the litter box, including soiled absorbent material and unsoiled absorbent material, has to be discarded.
Currently clumping clays and other water absorbent material are used to improve litter compositions. An improved composition for animal litters uses the clayey soils or comminuted rocks, e.g. the sodium bentonites, comprising at least one water-swellable clay mineral in the montmorillonite clay family. These absorbent materials not only absorb liquid dross, but they aid in the identification of used litter from unused litter portions. These absorbent materials have the ability to clump and harden after contact with an aqueous liquid such as urine thus facilitating the removal of only the soiled portion of the litter in a litter box or cage during cleaning without the necessity of removing all the litter. The wetted clump has the ability to group into a size substantially larger than the individual particles comprising the litter.
Though these improved compositions have eased the owners' task of removing soiled litter portions, they are still short of addressing problems associated with the burial or splitting of the clumped dross. The buried or split clump, if not timely discovered, will emit offensive odors within a relatively short period of time. Thus when the clumped dross is buried or split the homeowner must still either patiently sift through the litter to remove the used portions or simply discard the partially soiled litter. As a result, the benefits of having a clumped litter are diminished since the removal of the clumped dross once again becomes a time-consuming as well as costly process.
The following prior art references illustrate aspects of the technology of animal litter preparation, and, in particular, disclose the use of clays in such litters.
U.S. Pat. No. 4,685,420 issued Aug. 11, 1987 to Stuart, discloses an animal litter composition comprising a water-absorbing polymer such as a polyacryate combined with a porous inert solid substrate such as clay.
U.S. Pat. No. 5,000,115 issued Mar. 19, 1991 to Hughes, discloses the use of a water swellable bentonite clay as an absorbent litter material. The clay absorbs the liquids in animal waste which on contacting the clay agglomerates it into a stable mass easily separated from the unwetted and unsoiled portion of the composition.
U.S. Pat. No. 5,267,532 issued Dec. 7, 1993 to Franklin, et al., discloses a pH-indicating material maintained on an inert carrier that is separate from the cat litter material. The pH-indicating material has dual indicators that provide one color transition at a low pH and a different color transition at a high pH so that acidic or alkaline animal urine problems can be visibly detected upon contact between the animal urine and the pH-indicating material.
U.S. Pat. No. 5,371,054 issued Dec. 6, 1994 to Pluta, et al., discloses an animal litter composition used to diagnose animal health problems. The composition comprises at least one uncalcined clay substrate having a calcium oxide content of less than about 5% by weight and wherein the clay mineral component of said substrate has an attapulgite content of at least about 35% by weight, in combination with at least one chemical pH indicator.
U.S. Pat. No. 6,619,233 issued Sep. 16, 2003 and U.S. Pat. No. 6,763,783 issued Jul. 20, 2004 both to Mochizuki, disclose a granulated-type, urine-discharge processing material for animals that discriminates between before-use and after-use. The material comprises a water absorbent granular body dyed with water soluble dyes or a water absorbent granular body containing powder of water soluble dyes, and a water absorbent surface layer covering a surface of the water absorbent granular body. The water absorbent surface layer and the water absorbent granular body are bonded to each other through a non-continuous water soluble adhesive layer formed of a plurality of adhesive non-coated parts and a plurality of adhesive coated parts which is coated on the surface of the water absorbent granular body. Discharged animal urine is permeated into the water absorbent granular body through the water absorbent surface layer and the non-continuous water soluble adhesive layer, or by dissolving the adhesive coated parts. Thereby, the water soluble dyes are eluted into the discharged urine so that the water absorbent surface layer is dyed through the non-continuous water soluble adhesive layer. The water absorbent granular body is chiefly composed of vegetable fiber or vegetable powder and contains inorganic fillers. The water absorbent granular body further contains powder of a water absorbent polymer so that the granular body can have rich water absorbing and retaining properties. No mention is made to clays in the patent.
A need exists for a clumping litter that clumps in response to wetness and can be readily discovered and removed from the remaining dry litter when clumped and wet.